The present invention relates generally to fuel-fired heating appliances, such as furnaces and water heaters. More specifically, embodiments of the invention provide an improved burner assembly for a fuel-fired heating appliance.
In fuel-fired heating appliances such as, for example, air heating furnaces, a known firing method is to flow a fuel/air mixture into a burner box containing a burner, which is conventionally an elongated flat or curved single mesh. An associated igniter is also disposed in the burner box and is operative to combust the fuel/air mixture, thereby creating hot combustion gases used to heat air (or another fluid as the case may be) for delivery to a location served by the heating appliance. Typically, the furnace includes a series of heat exchanger combustor tubes, externally across which the fluid to be heated is flowed. Spaced apart open inlet portions of these combustor tubes extend through corresponding openings in a wall of the burner box which faces the burner, and thus the hot combustion gases are flowed through the combustor tubes. The hot combustion gases are discharged from the heating appliance into a suitable flue structure. At the same time, a blower portion of the furnace forces air being recirculated to and from a conditioned space served by the furnace externally over the heat exchanger combustor tubes to transfer combustion heat therefrom and thereby heat the recirculating air.
In this regard, FIG. 1 is a schematic cross-sectional view of a portion of a combustion section 10 of a prior art fuel-fired heating appliance. Combustion section 10 includes, from left to right in FIG. 1, a burner box 12, a heat exchanger assembly 14, and a collector box 16, joined together as indicated. As shown, burner box 12 forwardly terminates at a rear wall 18 of heat exchanger assembly 14, and heat exchanger assembly 14 forwardly terminates at a rear wall 20 of collector box 16.
Heat exchanger assembly 14 includes five combustor tubes 22. Combustor tubes 22 extend through the interior of heat exchanger assembly 14 and have open inlet ends 24 supported in corresponding openings in rear wall 18 and open outlet ends supported in corresponding openings in rear wall 20. As can be seen in FIG. 1, the open rear inlet ends 24 of combustor tubes 22 are interdigitated with imperforate sections 28 of rear heat exchange assembly wall 18. An inlet 30 of a draft inducer fan is positioned in collector box 16.
Referring also to FIG. 2, a rectangular, flat metal mesh burner 32 is positioned in burner box 12 in a spaced, facing relationship with the open inlet ends 24 of combustor tubes 22. As is well known, burner 32 provides a flame attachment structure and facilitates controlled combustion in burner box 12. Burner 32 is carried within a suitable frame 34 secured to an interior flange portion 36 of burner box 12. An igniter 38 extends into burner box 12 and is operatively associated with burner 32.
During firing of the heating appliance with which burner 32 is associated, a flow 40 of pre-mixed fuel and air is forwardly drawn through burner box 12 to burner 32. At this point, the flow 32 is caused to combust by igniter 38 to form an elongated reaction flame pattern 42 emanating from the downstream side of burner 32. As shown in FIG. 1, portions of the flame pattern 42 are drawn into combustor tubes 22 and form therein hot combustion gases 44. The balance of the flame pattern 42 is directed against wall 18.
At the same time, air 46 (or another fluid) is suitably flowed externally across combustor tubes 22 to create heated air 48 for delivery to a conditioned space served by the heating appliance. The draft inducer fan draws cooled combustion gases 50 from combustor tube outlet ends 26, through the interior of collector box 16, into inlet 30, and eventually exhausts the cooled combustion gases 50 to a suitable flue.